Poly SY20 USB-A Replacement Battery 3.7V 2600mAh Li-ion

Plantronics Poly SY20 USB-A — 3.7V Li-ion Replacement Battery

This 3.7V, 2600mAh (9.62Wh) Li-ion cell replaces the internal battery in the Poly SY20 USB-A speakerphone. The SY20 is a portable Bluetooth conference speaker — when the original cell degrades, audio cuts out early or the unit fails to hold a charge. This replacement restores wireless operation without buying a new unit.

• Poly SY20 USB-A fit: The SY20 runs a single Li-ion cell at 3.7V nominal. The BMS on this unit monitors cell voltage closely — a degraded cell that sags below threshold triggers an early shutdown even when the indicator still shows partial charge. This cell matches the voltage rail and physical dimensions (66.00 × 21.70 × 20.00mm) required by the SY20 housing.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SY20 platform. The BMS accepted the cell without error, balanced charge terminated cleanly at full voltage, and audio output remained stable through the draw cycle.
• Fuel gauge reset after install: Once fitted, run the SY20 down to automatic shutdown before recharging to full. Skipping this step leaves the fuel gauge calibrated to the old degraded cell — the indicator will read inaccurately and early shutoffs will continue despite the new cell being healthy.

Why the SY20 cuts out at high volume even with a charged battery

At high volume, the SY20 amplifier pulls a sharp current spike on top of the Bluetooth radio draw. A degraded or low-capacity cell cannot sustain that combined load — voltage sags below the BMS cutoff threshold and the unit shuts down mid-audio. This is not a software fault. It is a cell voltage problem. A fresh 2600mAh cell at 3.7V holds the rail stable through those combined amp and radio current peaks.

Audio distorting before the battery indicator reaches empty

Distortion before the battery reads empty is a voltage sag symptom, not a speaker fault. As the cell discharges, internal resistance rises — under amplifier load, terminal voltage drops below the clean audio threshold before the indicator registers empty. The amplifier clips the signal because rail voltage is insufficient, producing the distortion. After fitting this replacement cell, if distortion persists, confirm the SY20 firmware is current and run one full discharge cycle to recalibrate the fuel gauge to the new cell's actual capacity curve.